Implant system and method to treat degenerative disorders of the spine

ABSTRACT

An implant has a first hook and a second hook. A connector is coupled to the first and second hooks. The implant is adapted in a preferred embodiment to hook and look onto a spine.

CLAIM OF PRIORITY

This application claims benefit to U.S. Provisional Application No.60/801,871, filed Jun. 14, 2006, entitled “Implant Positioned Betweenthe Lamina to Treat Degenerative Disorders of the Spine,” which isincorporated herein by reference and in its entirety.

CROSS REFERENCES TO RELATED APPLICATIONS

This application relates to, and incorporates herein by reference, eachof the following in its entirety: U.S. patent application Ser. No.11/761,006, filed Jun. 11, 2007, entitled “Implant System and Method toTreat Degenerative Disorders of the Spine,” (Attorney Docket No.:SPART-01018US1); and

U.S. patent application Ser. No. 11/______, filed Jun. ______, 2007,entitled “Implant System and Method to Treat Degenerative Disorders ofthe Spine,” (Attorney Docket No.: SPART-01018US3).

BACKGROUND OF INVENTION

The most dynamic segment of orthopedic and neurosurgical medicalpractice over the past decade has been spinal devices designed to fusethe spine to treat a broad range of degenerative spinal disorders. Backpain is a significant clinical problem and the annual costs to treat it,both surgically and medically, is estimated to be over $2 billion.Motion preserving devices to treat back and extremity pain have,however, created a treatment alternative to fusion for degenerativedisc-disease. These devices offer the possibility of eliminating thelong term clinical consequences of fusing the spine that is associatedwith accelerated degenerative changes at adjacent disc levels.

While total disc replacement is seen as a major advance over fusion, theprocedure to implant the devices in the lumbar spine requires a majoroperation via an anterior approach, subjecting patients to the risk ofsignificant complications. These include dislodgement of the device,which may damage the great vessels, and significant scarring as aconsequence of the surgical procedure itself, which makes revisionsurgery difficult and potentially dangerous. Thus, there are advantagesto spinal implants that can be inserted from a posterior approach, atechnique with which spine surgeons are much more experienced. Theposterior surgical approach also has the benefit of being able todirectly address all pathologies that may be impinging the neuralelements, which is not possible from an anterior approach. Motionpreserving spinal devices that can be implanted with a minimallyinvasive, posterior procedure offer the benefit of less surgical traumaand faster patient recovery and also offer cost savings to payers withpatients staying fewer days in the hospital.

Motion preserving devices placed posteriorly typically either rely onthe spinous processes to support the implant or require pedicle screwsto be inserted. However, spinous processes are not load bearingstructures and are not rigid. In a population of patients with backpain, the laminae offer a much stronger structure to position animplant, since they consist of significantly stronger bone, and thelaminae are also closer to the spine's axis of rotation. Pedicle screwshave several disadvantages when used as attachments for motionpreservation devices. The procedure to implant them is considered majorsurgery requiring a wide exposure. The screws are also subject tosignificant loads and screw loosening is a known consequence over timein these cases. Removing the screws and fusing the spine requires majorrevision surgery.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a perspective view of an embodiment of the dynamic spinestabilization, motion preservation implant of the invention.

FIG. 2 is a perspective view of another embodiment of the dynamic spinestabilization, motion preservation implant with pedicle screws of theinvention.

FIG. 3 is a side view of an embodiment of a hook of the invention of theembodiment of FIG. 2.

FIG. 4 is a top view of the embodiment of the hook of the embodiment ofthe invention of FIG. 3.

FIG. 5 is an end view of the embodiment of the hook of the embodiment ofthe invention of FIG. 3.

FIG. 6 is a bottom view of the embodiment of the hook of the embodimentof the invention of FIG. 3.

FIG. 7 is a side perspective view of the embodiment of the hook of theembodiment of the invention of FIG. 3.

FIG. 8 is a side perspective view of another embodiment of the hook ofthe invention.

FIG. 9 is a top view of the embodiment of the invention of FIG. 8.

FIG. 10 is a side view of the embodiment of the invention of FIG. 8.

FIG. 11 is a side partially sectioned view of another embodiment of animplant of the invention.

FIG. 12 is a side view of an embodiment of a hook of the embodiment ofthe invention of FIG. 11.

FIG. 13 is a perspective view of a hook with barbs of an embodiment ofthe invention to be used with the embodiment of the invention of FIG.11.

FIG. 14 is a side view of the embodiment of the hook of the invention ofFIG. 13.

FIG. 15 is a side view of another embodiment of the hook of theinvention.

FIG. 16 is a side view of the another embodiment of the hook of theinvention of FIG. 15 in a different orientation.

FIGS. 17A, 17B are schematical top views of the embodiment of FIG. 15.

FIGS. 18A, 18B are side views of another embodiment of the hook of theinvention.

FIG. 19 depicts an embodiment of the method of implantation of theinvention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

In one embodiment of the present invention, an implant is provided thatcan be placed between the lamina through a posterior, minimally invasivesurgical technique and is designed to treat degenerative disorders ofthe spine. Degenerative disc disease results from the natural process ofaging and ultimately affects all structures of the vertebral motionsegment. The degenerative process causes loads that are normally borneby the intervertebral disc to be transferred to the articular facetjoints, ligaments and other soft tissues of the spine.

The benefits of this implant are: The articular facets provide anexcellent structure to which to attach an implant. They consist of verystrong cortical bone, the strongest in the lumbar vertebra. There are nomajor nerves or vessels in the area approximate to the lateral aspect offacets, making them also a very safe point of attachment.

Attached to hooks, a crosslink can be positioned as far anterior as ispossible without actually impinging on the spinal canal.

The implant can be inserted through two small incisions on either sideof the mid-line, preserving the spinal ligament structures, includingthe supraspinous ligament and the interspinous ligament and permittingthe implant to placed using a minimally invasive procedure.

An embodiment of the clamp implant system 20 of the invention isdepicted in FIG. 1. Implant system 20 provides for dynamic stabilizationand motion preservation of the spine. Implant system 20 includes anchorsystems 22, horizontal rods 24, 26 and vertical connector system 28.Preferably, the anchor systems 22 and the vertical connector system 28are made of titanium although stainless steel can also be used. Thehorizontal rods 24, 26 are preferably made of PEEK or other similarpolymer as described below or are made of a super elastic material suchas Nitinol which is an alloy of titanium and nickel. Other biocompatiblematerials can be used and be within the spirit and scope of theinvention. Preferably, the vertical system 28 is rigid while thehorizontal rods 24, 26 are flexible. Such a system 20 would accordinglyhave the horizontal rods made of PEEK or a similar polymer or a superelastic material while the vertical system is comprised of titanium orstainless steel. With such a system, the load that the spine places onthe system would be absorbed by the horizontal rods causing thehorizontal rods to flex while the vertical system remains rigid.

FIG. 2 includes another embodiment of the clamp implant system 20 whichhas an additional provision for pedicle screws 38 to assist in holdingthe system 20 to the spine. Elements of the embodiment of FIGS. 1, 2that are the same have similar numerical references.

Generally, the clamping implant system 20 (FIGS. 1, 2) includes opposingclamps 30, 32 that can wrap around the facets (from posterior toanterior) and hook or angle under the facets to assist in maintainingthe clamps in position and resist pull-out forces. Accordingly, theclamps 30, 32 hook or angle around the outside of the facets and areheld in place by the design of the clamps 30, 32. The system 20 alsoincludes opposing clamps 34, 36 which are the similar to opposing clamps30, 32. The clamps 30, 32, 34, 36 have set screws 40 as explained belowto lock in the horizontal rods 24, 26.

The opposing clamps 30, 32, and opposing clamps 34, 36 as can be seen inFIGS. 3, 4, 5, 6, 7, include a head 42 and a foot or hook 44.Preferably, the clamps are of one piece construction, however, asdescribed below, the clamps can be of several piece construction withthe added advantage of more degrees of freedom in implanting the clampsin the patient. The clamps 30, 32, 34, 36 include a threaded set screwbore 46 for receiving the set screw 40 and a horizontal rod bore 48 forreceiving the horizontal rods 24, 26. The head 42 also includes apedicle screw bore 50 which is preferably unthreaded and which canreceive the pedicle screw 38. The bore 50 is angled in order to guidethe pedicle screw into the pedicle of the spine. The head 42,accordingly, accepts in this embodiment a horizontal rod that istransversely mounted in the head and the top mounted set screw 40. Aswill be discussed below, the head 42 can include a split retainer, suchas a split ball retainer that has a central bore for accepting thehorizontal rod, and, which split retainer can be compressed by the setscrew to retain the horizontal rod in the head of the clamp. The foot44, points like a finger away from the head and in FIG. 3 looks muchlike an index finger of a right hand of a human extending from the restof the hand, with the fingers and thumb of the rest of the hand foldeddown into the palm of the human hand. Stated another way there is anL-shaped junction between the head 42 and the foot or hook 44. As isevident from the figures, there is in this preferred embodiment, acontinuous transition from the head 42 to the foot or hook 44. The innersurface of the foot 44 can be comprised of a textured surface to providefor bony ingrowth of the spine bone into the foot 44. Also the innersurface can be coated with bone growth inducing materials such as bonemorphogenetic proteins or BMPs. The inner surface of the foot 44 in thispreferred embodiment, is comprised of a compound surface that canaccommodate the anatomical shape of the facets in order to secure theclamps about the facets. In this embodiment, the foot 44 has a firstradius of curvature 52 (FIG. 5) which defines the first curve of thefoot along the length of the foot. The foot 44 also includes a secondradius of curvature 54 (FIG. 6) which defines the second curve of thefoot across the width of the foot with the first curve and the secondcurve in this embodiment being about perpendicular to each other. Thefirst curve runs about vertically and the second curve runs abouthorizontally. In this embodiment the first radius of curvature is about0.625 inches and the second radius of curvature is about 0.785 inches.These curves allow the foot or hook 44 to optimally conform to theanatomical shape of the outside of the facet with a contour for maximumcontact area. In this preferred embodiment, the clamps 30, 32, 34, 36have about up to 40 degrees of adjustment upon implantation relative tothe coronal orientation of the spine and up to about 10 degrees ofadjustment upon implantation relative to the sagittal orientation of thespine.

As can be seen in FIGS. 3, 5, 6, spikes 56 extend from the inner surfaceof the foot or hook 44 of the clamps 30, 32, 34, 36. These spikes 56 areused to also secure the foot or hook 44 to the outer surface of thefacets. The tips of the spikes 56 are designed to cut and penetrate thefacet bone and not to compress the facet bone. The spikes have flatsurfaces 58 that increase lateral resistance to lateral movement of theclamps 30, 32, 34, 36, and, thus, assist in preventing the clamps fromworking themselves out of engagement with the facets. The spines 58 arearranged down the length of the foot 44 and across the base of the foot44, where the foot 44 transitions to the head 42. As depicted, thespikes 56 are arrayed in the foot in order to obtain optimal stabilityof the clamp as secured to the facets. The smooth transition between thehead 42 and the foot 44 allows for, in this embodiment, continuoussagittal adjustment. This additionally allows for optimal positioningand orientation of the horizontal rods 24, 26 upon implantation of thesystem 20. The shape and radii of the foot and the transition from thehead to the foot allow the clamp to match the anatomical variations inthe junction between the transverse process and articular processes ofthe spine.

FIGS. 8, 9, 10, depict alternative embodiments of the clamps 30, 32, 34,36, which have lamina articular process hooks 60, 62 which have a hookelement 64, 66, respectively, that is curved to fit around the laminaand assist in holding the clamp in place in the spine. The hooks 60, 62include adjustable arms 68, 70 that can adjust to the size of the laminaof the spine. As is evident from FIGS. 8, 9, 10, each arm 68, 70includes an elongate slot such as slot 72 with a set screw such as setscrew 74, provided through said slot 72. The set screw 74 is mounted ina threaded bore in the clamp 30 and the arm 68 can slide relative to therest of the clamp to adjust to the spine and then the arm 68 can belocked into position by the set screw. It is evident from the depictionthat clamp 30 in FIGS. 8, 9, 10, has a different head than the headdepicted in the prior embodiment of the clamp 30. In order toaccommodate the laminar hooks 60, 62, the embodiments of the clamp 30 inFIGS. 1-7 can be modified in a number of ways. For example, the top ofthe head of the clamp in these figures can be widened to accept the arm68 and the set screw 74, and, thus, both the set screw 40 and the setscrew 74, can be tightened from the top of the head of the clamp.Alternatively, the slot 72 of the arm can be rotated by about ninetydegrees so that the set screw can lock the arm to the clamp along theoutside of the clamp, opposite to the surface of the clamp that has thespines and conforms to the surface of the facet. It is also to beunderstood that the clamps 30, as they appear in FIGS. 8, 9, 10, can beused by themselves to repair fractures of the pars interarticularis onthe lamina of the spine.

The horizontal rods 24, 26 can have variable lengths and diameters inorder accommodate the shape of the spine. Preferably, the diameters ofthe horizontal rods 24, 26 can be selected to adjust the dynamicstabilization, motion preservation feature afforded by theseembodiments. Larger diameter, generally, will provide for a stiffersystem while smaller diameters will provide for a less stiff system. Forthe same diameter, rods made of PEEK will provide for a stiffer systemthan rods made of a super elastic material. Also rods made of stainlesssteel will be stiffer than rods made of titanium. PEEK rods will be lessstiff than rods made of titanium or stainless steel. Accordingly, therods can be selected to give the degree of flex desired, and, thus, thedegree of dynamic stabilization desired in response to dynamic loadsplaced on the system 20 by the spine in motion. It is to be understoodthat the horizontal rods can also be bent or bowed out in order toaccommodate the anatomical structures of the spine.

The vertical connector system 28 in FIGS. 1, 2, connect adjacenthorizontal rods 24, 26, which horizontal rods are associated withdifferent vertebral levels. In this embodiment the vertical connectorsystem 28 is about U-shaped. The vertical connector system 28 includesan upper half connector 76 joined to a lower half connector 78, alongthe split line 86, by a locking screw 80. With the upper connector andthe lower connector joined, the system 28 defines a first horizontal rodcapture bore 82 and a second horizontal rod capture bore 84. Thevertical connector systems 28 are curved at the midpoint or apex of thecurve in order to accommodate, and, thus, preserve the spinous processesand the associated ligaments. In this particular embodiment, the lockingscrew 80 is located at the midpoint and is used to lock the system 28about the first and second horizontal rods 24, 26. It is to beappreciated that another vertical connector system 28 can be used withthe system 20 in order to impart additional stiffness. If two systems 28were used, one would be closer to the first clamp 30 (also clamp 34) andthe other would be closer to the second clamp 32 (also clamp 36) inorder to accommodate the spinous processes and ligament structures ofthe spine. If two systems 28 were used, the set screws 80 and themidpoint or apex of each system would be closer to the respective clampsin order to define a large opening between the two vertical connectorsystems 20 to accommodate the spinous processes and associatedligaments. If desired, the vertical connector system can be made of aless stiff biocompatible material as discussed herein, should additionalflexibility be desired.

Referring to FIGS. 11, 12, another embodiment of the present inventionis an implant, generally denoted as 100, with a first hook 102, a secondhook 104 and a cross-link or horizontal rod 106 coupled to the first andsecond hooks 102 and 104. The first and second hooks 102 and 104 havegeometries that conform to a lateral border of a superior articularfacet.

In various embodiments, the implant (i) engages the laminae to stabilizethe spine in a dynamic manner, and (ii) can be made stiff enough torigidly stabilize the spine as an aid to a fusion.

In one embodiment, the first and second hooks have radii to provideconformance with the spine. As discussed below, the first and secondhooks 102 and 104 can be symmetrical in a sagittal orientation and freeto rotate around a coronal axis. The first and second hooks 102 and 104,can provide an ability to adjust to, and be affixed to, the articularfacets. In one embodiment, the first and second hooks 102 and 104include at least one member to engage with the articular facet. Thismember can be a fin, stud, spike, and the like, as discussed above withrespect to other embodiments.

Further as seen in FIGS. 11, 12, the hooks include a ventral or lowerhooked section 108 and an dorsal or upper head section 110. The hookedsection 108 can conform to the spine as described herein and the headsection 110 can mount the cross-link or horizontal rod 106. The headsections 110 can include a top bore 112 that is threaded and can accepta set screw to lock the horizontal rod 106 in place. The head section110 also includes either (1) a recess 114 that can receive an end of thehorizontal rod 106 such that the set screw can lock the rod 106 inplace, or (2) a bore 116 through which the rod 106 can be received sothat the spacing between the hooks 102, 104 can be adjusted. Once therod 106 is received in the bore 116 and the spacing of the hooks 102,104 is adjusted by sliding the hook 102 on the rod 106, a set screw canbe used to lock the rod 106 in place. It is to be understood, thatprocedurally and preferably, the hooks 102, 104 are placed adjacent tothe facets and the length between the hooks is adjusted prior to thetightening of the set screws to lock the rod 106 and the hooks 102, 106together. Alternatively, the rod 106 can be telescoping such that afirst portion 118 of the rod 106 can slide into a second portion 120 ofthe rod 106 in order to adjust the length of the rod 106. If desired, anadditional set screw can be mounted on the second portion 120 of the rod106 to lock the first portion to the second portion of the rod.

As illustrated in FIGS. 13, 14, 15, 16, 17A, 17B the first and secondhooks such as hook 102 can have a ventral or lower section 108 anddorsal or upper sections 110 that can move and in this embodiment,rotate relative to each other. The ventral or lower hooked sections 108has a freedom of motion about an axial plane to allow for variations inanatomy of the articular facet. The dorsal or upper section 110 acceptsthe horizontal rod 106. The dorsal or upper section 110, as previouslydiscussed, includes a recess or bore to accept the horizontal rod 106.In this embodiment, the horizontal rod 106 rests in the saddle or heador upper portion 110 and a set screw locks the horizontal rod in placein the head.

As depicted in FIGS. 15, 16, 17A, 17B, the lower hooked portion 108 canrotate relative to the upper head portion 110. The rotation occurs atsplit line 122. Preferably, the upper portion 110 can snap into thelower portion 108 and be captured under a lip of the cylindrical recessof the lower portion 108. Thus, the upper portion 110 can rotate in therecess 122 of the lower portion 108 at the split line 122. If desiredthe rotation can be limited by a limit rod 126 that is mounted on thelower portion 108 and projects through the cylindrical recess 122. Theupper portion includes an enlarged bore 128 through which the limit rod126 is received, when the upper portion is assembled with the lowerportion of the hook 102. In a preferred embodiment, the limit rod allowsthe upper portion of the hook 102 to rotate about 15 degrees on eachside of a central axis, for a total of about 30 degrees of rotation. Itis to be understood that 360 degrees of rotation is possible with thelimit rod 126 removed, and also that changes to the size of the bore 128can be made to adjust the degree of rotation of the upper portion to thelower portion or the hook 102. Accordingly, the first and second hooks102 and 104 illustrated in FIGS. 15, 16 are adjustable and can bere-adjusted after the hooks 102 and 104 are initially implanted.

In the embodiment of FIGS. 18A, 18B, the horizontal rod 106 isconfigured to be fixed with compression applied by a set screw receivedthough bore 112 in head 1110. The set screw can fix an orientation ofthe ventral or upper section 108 of the hooks 102 and horizontal rod106, as well as, lock the upper portion of the hook to the lower portion108 at the same time. In this embodiment, the horizontal rod 106 can bereceived in a compression block 130 that is received in the bore 112.Generally, the compression block is cylindrical and can be comprised oftwo pieces which mate with facing recesses that can receive thehorizontal rod 106. Alternatively, the compression block can be a onepiece construction with a slit. In either embodiment, the set screw,when turned down in the bore 112, causes the compression block 130 tocompress about, and without causing damage to, the horizontal rod 106 tolock the rod in place.

In one embodiment, the horizontal rod 106 has a flat surface thatconforms to a laminar anatomy or a contoured surface to match thelaminar anatomy.

In another embodiment of the present invention, the implant 100 includesan artificial ligament attached to the horizontal rod 106. Theartificial ligament can be looped around the superior spinous processand then re-attached to the horizontal rod 106. The artificial ligamentprovides a limit to flexion and increases rigidity of the implant. Theartificial ligament can be made of a biocompatible material.

In another embodiment of the present invention, an implant assembly isprovided that has first and second implants 100. The first and secondimplants 100 can be coupled by at least one vertically running rodconfigured to provide rigid stability as an aid in fusing the spine.

It is to be understood that the various features, designs and functionsof the various embodiments can be selected for and or combined in otherembodiments as is advantageous.

With respect to the method of implantation (FIG. 19), the hooks can beplaced adjacent to the facets, and then the position of the horizontalrod relative to the hooks can be adjusted. The hooks can be pressed intothe bone and the set screws can be tightened to hold the hooks andhorizontal rod in place. With two such configurations in the spine, theconfigurations can be connected with vertical rods and the like.Alternatively, the implant, including the hooks and the horizontal rodloosely coupled together, can be inserted as an assembly and then oncepositioned, the set screws can be tightened to lock the system 100 inplace in the spine.

Materials for use with the implant include the following:

As indicated above, the implant can be made of titanium, stainlesssteel, super elastic materials and/or polymers such as PEEK.

In addition to Nitinol or nickel-titanium (NiTi) other super elasticmaterials include copper-zinc-aluminum and copper-aluminum-nickel.However for biocompatibility the nickel-titanium is the preferredmaterial.

Other suitable material include, by way of example, onlypolyetheretherketone (PEEK), polyetherketoneketone (PEKK),polyetherketone (PEK), polyetherketoneetherketoneketone (PEKEKK), andpolyetheretherketoneketone (PEEKK). Still, more specifically, thematerial can be PEEK 450G, which is an unfilled PEEK approved formedical implantation available from Victrex of Lancashire, GreatBritain. (Victrex is located at www.matweb.com or see Boedekerwww.boedeker.com). Other sources of this material include Gharda locatedin Panoli, India (www.ghardapolymers.com).

Preferably, the horizontal rods are made of PEEK or a similar polymer ora super elastic material, which materials are flexible, or the rods aremade of another flexible material, and the anchors and the verticalsystems are made of titanium or stainless steel which are stiff or madeof another stiff material.

Further, it should be apparent to those skilled in the art that variouschanges in form and details of the invention as shown and described maybe made. It is intended that such changes be included within the spiritand scope of the claims appended hereto. The foregoing description ofpreferred embodiments of the present invention has been provided for thepurposes of illustration and description. It is not intended to beexhaustive or to limit the invention to the precise forms disclosed.Many embodiments were chosen and described in order to best explain theprinciples of the invention and its practical application, therebyenabling others skilled in the art to understand the invention forvarious embodiments and with various modifications that are suited tothe particular use contemplated. It is intended that the scope of theinvention be defined by the claims and their equivalents.

1. An implant comprising: a first bone anchor adapted to be attached toa first portion of a vertebra; a second bond anchor adapted to beattached to a second portion of the same vertebra; a flexible horizontalrod connected to the first bone anchor through a first head of the firstbone anchor said flexible rod connected through a second head of thesecond bone anchor; and said first bone anchor including a first uppercradle and a first lower cradle to capture the flexible horizontal rodbetween the first upper cradle and the first lower cradle and the secondbone anchor includes a second upper cradle and a second lower cradle tocapture the flexible horizontal rod between the second upper cradle andthe second lower cradle.
 2. The implant of claim 1 including a firstlock to lock the first bone anchor to the horizontal rod and a secondlock to lock the second bone anchor to the horizontal rod and whereinthe locking of the first and second bone anchors to the horizontal rodwith the first and second bone anchors positioned relative to onevertebra locks the implant to the one vertebra.
 3. The implant of claim1 wherein said first bone anchor includes said first head which is anupper portion that can accept the flexible horizontal rod and said firstbone anchor includes a lower portion extending from said upper portionwhich lower portion is adapted to engage bone.
 4. The implant of claim 3wherein the one of the upper portion and the lower portion of the firstbone anchor can move relative to the other of the upper portion and thelower portion of the first bone anchor.
 5. The implant of claim 1wherein said horizontal rod is adapted to be about parallel to thevertebra with the first anchor secured to a first portion of thevertebra and the second anchor secured to a second portion of thevertebra located distally from the first portion of the vertebra.
 6. Theimplant of claim 1 wherein said horizontal rod is made of PEEK.
 7. Animplant comprising: a first bone anchor adapted to be attached to afirst portion of a vertebra; a second bond anchor adapted to be attachedto a second portion of the same vertebra; a flexible horizontal rodconnected to the first bone anchor and the second bone anchor; a thirdbone anchor adapted to be attached to a first portion of anothervertebra; a fourth bone anchor adapted to be attached to a secondportion of the same another vertebra; another flexible horizontal rodconnected to the third bone anchor and the fourth bone anchor; a rigidvertical rod connected between the first horizontal rod and the secondhorizontal rod.
 8. The implant of claim 7 wherein said rigid verticalrod is not meant to flex, while at least of the first and secondhorizontal rods is meant to absorb and be deflected with respect to atleast in part the motion of the spine.
 9. The implant of claim 7 whereinsaid rigid vertical rod is curved so as to be adapted to avoid a spinousprocess of a spine which is located between the flexible horizontal rodand the another flexible horizontal rod.
 10. The implant of claim 9including another rigid vertical rod that is curved so as to be adaptedto avoid a spinous process of a spine which is located between theflexible horizontal rod and the another flexible horizontal rod, withthe curved rigid rod and said another curved rigid vertical rod togetherdefining at least part of a circle.
 11. An implant comprising: a firstbone anchor adapted to be attached to a first portion of a vertebra; asecond bond anchor adapted to be attached to a second portion of thesame vertebra; and a flexible horizontal rod connected to the first boneanchor directly through a first head of the first bone anchor saidflexible rod connected directly through a second head of the second boneanchor, which flexible horizontal rod flexes to carry and accommodate aload placed on the implant by the spine.
 12. The implant of claim 11including: said first bone anchor including a first upper cradle and afirst lower cradle to capture the flexible horizontal rod between thefirst upper cradle and the first lower cradle and the second bone anchorincludes a second upper cradle and a second lower cradle to capture theflexible horizontal rod between the second upper cradle and the secondlower cradle.
 13. The implant of claim 11 including a first lock to lockthe first bone anchor to the horizontal rod and a second lock to lockthe second bone anchor to the horizontal rod and wherein the locking ofthe first and second bone anchors to the horizontal rod with the firstand second bone anchors positioned relative to one vertebra locks theimplant to the one vertebra.
 14. The implant of claim 11 wherein saidfirst bone anchor includes said first head which is an upper portionthat can accept the flexible horizontal rod and said first bone anchorincludes a lower portion extending from said upper portion which lowerportion is adapted to engage bone.
 15. The implant of claim 14 whereinone of the upper portion and the lower portion of the first bone anchorcan move relative to the other of the upper portion and the lowerportion of the first bone anchor.
 16. The implant of claim 14 whereinone of the upper portion and the lower portion of the first bone anchorcan rotate relative to the other of the upper portion and the lowerportion of the first bone anchor.
 17. The implant of claim 11 includinga first lock to lock the first bone anchor to the horizontal rod and asecond lock to lock the second bone anchor to the horizontal rod andwherein the locking of the first and second bone anchors to thehorizontal rod with the first and second bone anchors positionedrelative to one vertebra locks the implant to the one vertebra.